hi Experts,

I need your help. 

We are migrating from Service Manager to SMAX. 

I know that SMAX is not Service Manager, however we need to do some customization & we are finding it difficult in SMAX because it doesn't allow.

In SM, the Service Request priority is derived from the Categorization (Category, Subcategory, Product type, & classification (custom table)). 

We want to achieve that in SMAX, however the Record Category table is locked & cannot be modified.

I created a custom table that has all the Service Request categories in addition to the priorities. (note that i want to keep/use the main category field in the Request module, i also added another field called customCategory that is linked to the custom category table)

I have added a business rule that copies the value of the main category field to the custom category field after change. However when i select the category & save the record, on the custom category field it is showing "Not Available". 
It seems that the entity links work only on the Id field & the Id field is unique for each table.

My question is how to add a filter or query on entity link? 
For example, the Category field has a unique ID. This Unique ID i added in the custom category table. 
so my query will be, "select Priority from CustomCategory Table where entity.category.Id = entity.customcategory.customID"

Is there a way to achieve this?